Kopi tubruk, Indonesian coffee on its grounds
In Indonesia, the simplest coffee is made in the very glass it is drunk from: boiling water is poured over the powder, often already sweetened, and one waits for the grounds to settle. It is an infusion with no filter or apparatus, the kind served at street stalls, which gives a strong cup and leaves at the bottom a layer of grounds that is not drunk.
What happens in a glass of Indonesian coffee?
Start the scene or choose a stage. The animation simplifies the mechanism; what follows gives the details and the available references.
A fine powder, a little finer than table salt, and often sugar wait at the bottom of the glass. Nothing has been extracted yet.
Read the stages without animation
- The powder at the bottom of the glassA fine powder, a little finer than table salt, and often sugar wait at the bottom of the glass. Nothing has been extracted yet.
- Boiling water all at onceBoiling water is poured over all the powder at once. The powder rises to the surface, releasing its gases, then begins to get wet.
- Steeping in the glassThe powder bathes in all the water, which gradually takes on coffee. Extraction advances while the open glass cools, and slows down with it.
- The grounds settleThe water-soaked particles sink and form a layer at the bottom. The liquid clears at the top; the finest particles stay in suspension.
- Drinking, leaving the bottomOne drinks slowly, without stirring, and stops before the layer of grounds. The cup is strong but not very concentrated: the infusion has not reached its plateau, which comes at around twenty minutes.
To remember: Nothing separates the powder from the water: the grounds settle on their own, and one drinks before the infusion has given everything.
In history: A popular practice with no established date of origin; coffee trees were introduced to Java in 1696, then 1699.
Read the full article and its sources ↓History
Coffee reached Java through the Dutch. In 1696, plants from Kananur, on the Malabar coast, were planted near Batavia, then lost in an earthquake and a flood; in 1699, Henricus Zwaardecroon brought cuttings that took and became the stock of the Dutch East Indies coffees. The first Java coffee was sold at auction in Amsterdam in 1711 (source 1, ch. II and XX).
Cultivation then took place under compulsion. Under Marshal Daendels's plan, each Javanese family had to maintain a thousand bearing coffee trees and deliver two fifths of the harvest to the government warehouse; the Van den Bosch system reduced the obligation to 650 trees (source 1, ch. XX). Ukers says nothing about how the Javanese drank this coffee; he notes only that the Europeans of Java prepared a strong extract with the French filter, a spoonful of which they poured into hot milk (source 1, ch. XXXV).
The origin of the method itself is not dated. The oft-repeated idea that it came with merchants from the Middle East has no primary source in what could be read. The name comes from Javanese: kopi tubruk is, literally, the coffee “that collides,” the powder and the water thrown against each other, according to an Indonesian coffee website (source 6). Here it will be called glass coffee.
Indonesian universities now study it as a method in its own right. A team from Syiah Kuala University, in Aceh, describes it as a “simple and natural” technique in which hot water is poured over the powder in the cup, which is left to stand until the grounds have fully settled; it likens it to standardized professional cupping, which also steeps the powder directly in the bowl (source 2).
The motion
You need a glass or cup, a kettle and a spoon. The powder is fine, “a little finer than table salt” according to the Aceh study, which warns, after Kiki and colleagues, that an extra-fine powder overextracts and makes the cup very bitter (source 2). At a stall in Tulungagung, in eastern Java, boiling water is poured into a cup already filled with coffee and sugar (source 6).
The powder first rises to the surface, then gets wet and gradually sinks. One waits, without pressing or filtering, for the grounds to settle (source 2), then drinks slowly, leaving the layer at the bottom. For their trials, the Aceh researchers adopt the ratio of American professional cupping, 8.25 g for 150 mL of water at 93 °C: this is a protocol choice, not the measurement of a popular practice (source 2).
The settings
- GrindFine, a little finer than table salt (source 2).
- DoseNot documented for everyday use; 8.25 g for 150 mL in the Aceh study protocol (source 2).
- Brew ratioNot documented for everyday use; about 1 to 18 in the study protocol (source 2, calculation).
- TemperatureBoiling water at the stall (source 6); 93 °C in the study protocol (source 2).
- TimeUntil the grounds have settled (source 2); no timed duration found.
- PressureAtmospheric.
What it has going for it
- A glass and boiling water are enough: no filter, no apparatus, no consumable, which makes it the coffee of the humblest stalls and homes.
- The cup is strong and full-bodied: the Aceh study describes it as a drink with pronounced body and flavor (source 2).
- The method shows the coffee as it is, with no paper holding anything back, hence its kinship with professional cupping (source 2).
- It suits the country's coffees: in the Aceh study, tasters prefer, for color and aroma, the blends dominated by canephora, which according to the authors prevails in Indonesian habits (source 2).
What is held against it
- The yield is low: on a single Toraja arabica prepared five ways, a thesis from Gadjah Mada University measures for glass coffee the lowest concentration, 1.06% dissolved solids, and the lowest extraction, 16.5%, against 24.3% for a paper cone (source 3).
- The open glass cools during the wait, and water that cools extracts more slowly (source 4).
- A powder that is too fine overextracts and makes the cup very bitter (source 2).
- The grounds stay in the glass, and the unfiltered drink brings, like all preparations without paper, diterpenes that raise cholesterol (source 7); no measurement specific to this method was found.
What it gives in the cup
The grind commands the cup. In the Aceh study, on blends of arabica and canephora from Takengon, the fine powder yields significantly more extract than the coarse one, and particle size also changes the measured acidity, the pH ranging from 5.37 to 5.59; it changes the perceived color and aroma but not the taste scored by the panel (source 2).
The body is heavy and the cup not very clear, because nothing holds back the fines. Concentration nevertheless stays low: the Gadjah Mada thesis ranks it last of five methods, behind the French press and cold brew, which, like it, give lower phenolic compound contents that are close to one another (source 3). The physical principle partly explains it: in immersion, concentration rises then plateaus after about twenty minutes, and all the sooner the hotter the water (source 4); a glass drunk before this plateau has not extracted everything.
Anecdotes
- In Yogyakarta, Lik Man's stall, near Tugu station, run since the 1950s and taken over by him in 1969, serves kopi joss: a hot coffee into which a piece of still-glowing charcoal is dropped, whose name is said to imitate the sizzle, according to the province's tourism office (source 5).
The sources for this sheet
- William H. Ukers, All About Coffee, New York, The Tea and Coffee Trade Journal Company, 1922 (local transcription 1922_Ukers_All_About_Coffee_UTF8.txt), ch. II (introduction to Java), ch. XX (forced cultivation), ch. XXXV (European uses in Java) · online · primary
- Dian Hasni, Muhammad Haikal Irhamullah, Eva Murlida, Dedy Rahmad, “Identifikasi mutu kopi tubruk berdasarkan formulasi pencampuran dan ukuran kehalusan bubuk kopi,” Seminar Nasional Penelitian dan Pengabdian Teknologi Hasil Pertanian, Universitas Syiah Kuala, 2022 · online · primary
- Rahmatdita Hanifiantyo, Pengaruh Metode Penyeduhan Terhadap Karakteristik Fisikokimia Kopi Arabika Toraja, bachelor's thesis (skripsi), Universitas Gadjah Mada, 2026 · online · primary · reading: abstract only, recipe not read
- J. Liang, K. C. Chan, W. D. Ristenpart, “An equilibrium desorption model for the strength and extraction yield of full immersion brewed coffee,” Scientific Reports, 11, 2021, 6904, doi:10.1038/s41598-021-85787-1 · online · primary
- Dinas Pariwisata DIY (Yogyakarta tourism office), “Angkringan Lik Man,” Visiting Jogja, January 30, 2019 · online · secondary
- Toni Wahid, “Celebrating hundred years of kopi tubruk,” Cikopi, July 25, 2010 (blog) · online · secondary
- R. Urgert, M. B. Katan, “The cholesterol-raising factor from coffee beans,” Annual Review of Nutrition, 17, 1997, p. 305-324, doi:10.1146/annurev.nutr.17.1.305 · online · secondary · reading: abstract only (PubMed)